I have used flour but prefer corn meal. The flour tends to stick to the stone and is hard to brush off. It also leaves a white residue on the stone. Corn meal brushes off very easily and is also eaten by the critters. It is amazing how it brings up even the most hard-to-read inscriptions crystal clear. I carry a 5# bag of white corn meal, a soft brush, and a notebook in my car at all times. Y'never know when you'll want to make cornbread.....:-) Judy in Newnan